The invention concerns a system having an air-mass meter for an internal combustion engine in which the measurement place of the air-mass meter is located in a measurement tube.
For the regulating of internal combustion engines with fuel injection, it is necessary to measure the mass of air drawn in by the engine. Mechanical systems for this purpose are known which operate, for instance, with movable flaps or aperture plates which extend into the stream of air. Sensors are also known, for instance hot-wire air-mass meters, for the meaurement of the mass of air. They have the advantage that they have no moving parts and interfere less with the flow of air than the mechanical systems do. Furthermore, the result of the measurement is independent of differences in altitude, which is not true of the mechanical systems, which primarily measure the quantity of air.
Various different methods have been employed for the arrangement of the air-mass or air-quantity meters. Thus it is known, for instance, structurally to connect an air-mass meter operating by ultrasonics to an air filter. In this case, the measurement place of the air-mass meter is arranged within a short measurement tube which is concentric to the air filter. Due to the short length of the measurement tube, however, conditions of air flow at the measurement place are suitable only within limits, the limitation of suitable air flow being found under different operating conditions with the same mass flow. Therefore, the accuracy of the measurement does not meet all requirements.
It is therefore an object of the present arrangement to provide an arrangement with an air-mass meter in which suitable conditions of flow are assured within the meaurement tube, so that more accurate measurement results are obtained. The arrangement having the air-mass meter should be economical to manufacture, operate reliably and be suitable with respect to the space required as well as its ease of maintenance, for installation on an internal combustion engine, particularly that of an automotive vehicle.